For a site I'm building, I have to restrict the access to subparts of the site as follow

/ should be available to everyone being a valid user (easy to do)/customers should be available to members of the admin group/customers/customerA should be available to customerA only and members of admin group/customers/customerB should be available to customerB only and members of admin group/customers/customerC should be available to customerC only and members of admin groupand so on

All those users should be authenticated against a DB as they already exist in that DB for other services.